Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 210416
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
915 PM PDT MON OCT 20 2014

.DISCUSSION...WITH THE COOL POOL LOFT THERE IS INSTABILITY OVER THE
ENTIRE FORECAST AREA. WITH THE LIGHTNING ALREADY OCCURRING OVER THE
ARE AND SEVERAL SHORT WAVES STILL TO COME THROUGH HAVE ALREADY ADDED
ISOLATED THUNDERSTORMS TO AN UPDATE. AS SURFACE TEMPERATURES
CONTINUE TO COOL THIS INSTABILITY WILL DECREASE WITH JUST SHOWERS
REMAINING LATE THIS EVENING. SVEN

PREVIOUS DISCUSSION...THE FRONT HAS NOW PUSHED EAST OF THE CASCADES.
A COOL POOL ALOFT IS ALREADY STARTING TO MOVE INTO THE AREA AND
SHOWERS ARE DEVELOPING JUST WEST OF CRESCENT CITY. A COUPLE OF
LIGHTNING STRIKES HAVE BEEN OBSERVED OFFSHORE AND I WOULD NOT BE
SURPRISED IF WE SEE MORE STRIKES LATE THIS AFTERNOON THROUGH THIS
EVENING AS THE COOL POOL ALOFT REACHES THE COAST. THE MODELS SUGGEST
THE TROUGH WILL HAVE A SLIGHT NEGATIVE TILT AS IT MOVES INLAND THIS
EVENING AND AT THE SAME TIME THERE MAY BE ENOUGH INSTABILITY FOR A
FEW ISOLATED STORMS EAST OF THE CASCADES THIS EVENING. SHOWERS WILL
CONTINUE THROUGH AT LEAST THE FIRST HALF OF THE NIGHT, THEN WILL
DECREASE FROM WEST TO EAST AS THE TROUGH AXIS MOVES EAST OF THE
FORECAST AREA. WEAK SHORTWAVE RIDGING BUILDS INTO THE AREA TUESDAY
AND WE`LL GET A RELATIVE BREAK IN THE WEATHER. STILL COULD NOT RULE
OUT A FEW SHOWERS EARLY IN THE MORNING, OTHERWISE IT WILL BE DRY.
TEMPERATURES TUESDAY COULD END UP HIGHER THAN WHAT`S IN THE FORECAST
IF THERE`S ENOUGH BREAKS IN THE CLOUD COVER.

NEXT WE TURN OUR ATTENTION TO THE NEXT FRONT WHICH COULD IMPACT OUR
AREA WITH MODERATE TO HEAVY PRECIPITATION AND GUSTY WINDS. THE
MODELS ARE IN BETTER AGREEMENT COMPARED TO YESTERDAY WITH THE TIMING
OF THE FRONT. STEADY RAIN WILL START TO MOVE INTO THE NORTHWEST PART
OF THE FORECAST AREA WEDNESDAY MORNING, THEN SLOWLY MOVE SOUTH
DURING THE DAY. THIS FRONT WILL HAVE GOOD IV TRANSPORT AIMED RIGHT
AT THE COAST RANGE. SO IT`S NO SURPRISE THE MODELS PUT THE HEAVIEST
PRECIPITATION ALONG THE COAST AND COAST RANGE. IT`S A GOO BET 1-2
INCHES OR MORE WILL FALL IN THIS AREA WEDNESDAY. FURTHER SOUTH AND
EAST, SPECIFICALLY IN THE ROGUE VALLEY WE MAY NOT GET ANY MEASURABLE
RAIN FOR TWO REASONS. FIRST THE FRONT WILL BE SLOW TO MOVE
SOUTHEAST, SECOND WE`LL HAVE A DOWNSLOPE COMPONENT. I DID KEEP IT
DRY IN THE MORNING AND PUT IN A SLIGHT CHANCE MENTION IN THE
AFTERNOON.

THE FRONT WILL GRADUALLY MOVE SOUTHEAST WEDNESDAY NIGHT AND THE
FOCUS FOR MODERATE TO HEAVY PRECIPITATION WILL SHIFT SOUTH INTO THE
SOUTH COAST RANGE. ALSO, MODERATE PRECIPITATION WILL MOVE INTO THE
ROGUE VALLEY. RAINFALL AMOUNTS WEDNESDAY NIGHT AT THE COAST COULD
EASILY RANGE BETWEEN 2-4 INCHES AND 0.25-0.50 OF AN INCH IN THE
ROGUE VALLEY. THE FRONT WILL CONTINUE TO MOVE SOUTH INTO NORTHERN
CAL THURSDAY MORNING AND THE FOCUS FOR THE HEAVIEST RAINFALL WILL BE
IN WESTERN SISKIYOU COUNTY. WE COULD SEE IMPROVEMENT THURSDAY
AFTERNOON AND NIGHT, AT LEAST IN TERMS OF RAINFALL RATES WITH
PRECIPITATION EXPECTED TO BECOME LIGHT AND INTERMITTENT.

NEXT WE`LL ADDRESS THE WINDS. WINDS NEAR WEED HAVE DECREASE OVER THE
LAST FEW HOURS AND EXPECT THIS TREND TO CONTINUE INTO THIS EVENING,
THEREFORE WE`LL BE CANCELING THE WIND ADVISORY. MODERATE TO STRONG
WINDS ARE LIKELY AHEAD OF THE FRONT WEDNESDAY AND WEDNESDAY EVENING,
ESPECIALLY EAST OF THE CASCADES AND THEY COULD REACH ADVISORY OR
WARNING LEVELS NEAR AND JUST EAST OF SUMMER LAKE WEDNESDAY AFTERNOON
THROUGH THURSDAY MORNING. MODELS SHOW 700 MB WINDS INCREASING AND
PEAKING OUT BETWEEN 40-50 KTS WEDNESDAY NIGHT INTO THURSDAY MORNING.
ADDITIONALLY WINDS WILL CRANK UP IN THE SHASTA VALLEY NEAR WEED AND
THEY ARE ALSO LIKELY TO REACH ADVISORY CRITERIA. THE 700 MB WINDS
ARE MORE WESTERLY, BUT THE MEDFORD TO REDDING GRADIENT IS SUFFICIENT
ENOUGH FOR GUSTY WINDS. -PETRUCELLI

.LONG TERM...FRIDAY THROUGH MONDAY...A LARGE UPPER TROUGH WILL MOVE
TO AROUND 130W ON FRIDAY, AND A STRONG SHORTWAVE WILL ROUND ITS BASE
CAUSING THE TROUGH TO BECOME NEGATIVELY TILTED. SURFACE LOW PRESSURE
IS EXPECTED TO FORM UNDER THE AREA OF UPPER DIFFLUENCE AND MOVE
NORTH ALONG THE COAST. THIS WILL DRAG THE FRONT FROM THURSDAY BACK
NORTH AS A WARM FRONT ON FRIDAY. WHILE THERE ARE SOME MODEL
DIFFERENCES REGARDING THE SPECIFICS, THIS WILL LIKELY BRING RAIN TO
MUCH OF THE AREA, ESPECIALLY THE WEST SIDE AND SOUTH FACING MOUNTAIN
RANGES. IN FACT, DEEP, MOIST SOUTHWEST FLOW REMAINS AIMED AT THE
CURRY COAST AND MOUNTAINS AND WESTERN SISKIYOU MOUNTAINS AS THE
FRONT DROPS IN THURSDAY, AS IT LIFTS BACK NORTH AS A WARM FRONT
FRIDAY, AND INTO THE WEEKEND. THIS COULD BE A VERY BIG RAIN MAKER
FOR THESE AREAS AS THIS MOIST FLOW IS WRUNG OUT OVER THE TERRAIN.

THE KEY QUESTION REGARDING THE WINDS IS THE LOCATION AND STRENGTH OF
THE SURFACE LOW. THERE IS AT LEAST SOME POTENTIAL FOR STRONG WINDS
OVER THE WATERS, COAST, AND MOUNTAINS ON FRIDAY, BUT GIVEN THE
UNCERTAINTY OF THE LOW POSITION, WE WEREN`T ABLE TO GET SPECIFIC
JUST YET. WE DID RAISE THE POPS FOR FRIDAY, HOWEVER. THIS WILL NEED
TO BE WATCHED CLOSELY FOR WIND CONCERNS.

THE MAIN TROUGH AXIS MOVES INLAND SATURDAY WITH SHOWERS AND LOWER
SNOW LEVELS (AROUND 6000 FT). A WEAK RIDGE BUILDS IN ON SUNDAY WITH
LOWER CHANCES FOR RAIN. THE MODELS ALL ADVERTISE ANOTHER FRONT EARLY
NEXT WEEK, BUT DIFFER ON THE STRENGTH. WE`VE OBVIOUSLY TURNED A
CORNER INTO TYPICAL FALL WEATHER, AND THIS PATTERN LOOKS LIKE IT HAS
SOME STAYING POWER WHICH SHOULD HELP WITH OUR WATER ISSUES. -WRIGHT


&&

.AVIATION...21/00Z TAF CYCLE...LOW PRESSURE WILL MOVE ACROSS THE
AREA THIS EVENING WITH SCATTERED SHOWERS, A FEW ISOLATED
THUNDERSTORMS, AND MAINLY VFR CEILINGS. THERE WILL BE LOCAL MVFR
CEILINGS AND MOUNTAIN OBSCURATIONS IN THE VICINITY OF SHOWERS.
LATE TONIGHT INTO TUESDAY MORNING, ISOLATED SHOWERS WILL CONTINUE
WITH LOWERING CEILINGS IN VALLEYS WEST OF THE CASCADES LEADING TO
AREAS OF MVFR BETWEEN 12Z AND 17Z. CLOUDS WILL DIMINISH TUESDAY
MORNING INTO TUESDAY AFTERNOON BUT VFR CEILINGS WILL RETURN TO THE
COAST BY LATE AFTERNOON AND SPREAD INLAND TUESDAY EVENING. -DW

&&

.MARINE...UPDATED 600 PM PDT MON 20 OCT 2014...A SERIES OF
DISTURBANCES WILL IMPACT THE MARINE WATERS OVER THE NEXT WEEK.
A WEAK FRONT HAS BROUGHT SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS WITH SMALL CRAFT ADVISORY LEVEL SOUTH WINDS THAT WILL
PERSIST THIS EVENING OVER MOST OF THE WATERS NORTH OF CAPE BLANCO.
MEANWHILE, A LARGE LONG PERIOD WEST SWELL WILL REACH A PEAK THIS
EVENING AT AROUND 15 FEET.

LATE TONIGHT, WIND WAVES WILL DECREASE AND WESTERLY SWELL WILL BEGIN
TO GRADUALLY LOWER. BUT, SEAS WILL REMAIN STEEP AND ABOVE 10 FEET.
SOUTH WINDS WILL INCREASE TO SMALL CRAFT ADVISORY LEVELS AGAIN
TUESDAY MORNING WITH GALES LIKELY FROM LATE TUESDAY AFTERNOON ALL
THE WAY INTO WEDNESDAY EVENING AS THE STRONGEST FRONT OF THE WEEK
SLOWLY MOVES EAST. IT IS EXPECTED TO REACH THE WATERS WEDNESDAY
MORNING THEN MOVE INLAND WEDNESDAY EVENING. GIVEN THE SLOW MOVEMENT
OF THE FRONT, ALONG WITH HIGH END SMALL CRAFT TO GALE WINDS AND
BUILDING WEST SWELL, VERY STEEP AND CHAOTIC SEAS ARE EXPECTED WITH A
COMBINED HEIGHT OF 10 TO 13 FT ON TUESDAY BUILDING TO 15 TO 17 FT
WEDNESDAY.

THE HIGH AND STEEP WEST SWELL IS LIKELY TO BECOME DOMINANT AGAIN BY
THURSDAY. SWELL IS EXPECTED TO DIMINISH SLIGHTLY THURSDAY INTO
FRIDAY BUT THERE WILL BE A PERIOD OF MODERATE SOUTHWEST WINDS LATE
THURSDAY NIGHT INTO EARLY FRIDAY AS A WARM FRONT LIFTS ACROSS THE
WATERS. ANOTHER STRONG COLD FRONT MAY FOLLOW FRIDAY INTO SATURDAY.
/DW


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.


PACIFIC COASTAL WATERS...GALE WATCH FROM TUESDAY EVENING THROUGH
WEDNESDAY
     EVENING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT THIS AFTERNOON
FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM TO 11 PM PDT TUESDAY
     FOR PZZ356.
     HAZARDOUS SEAS WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
     EVENING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT TUESDAY
     FOR PZZ350-356.
     GALE WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR
     PZZ376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 9 AM TO 5 PM PDT TUESDAY
FOR
     PZZ376.
     HAZARDOUS SEAS WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     EVENING FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM PDT TUESDAY
     FOR PZZ370-376.
     GALE WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY AFTERNOON
     FOR PZZ370.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     PZZ350-370.
     SMALL CRAFT ADVISORY FOR WINDS FROM 9 AM TO 5 PM PDT TUESDAY
FOR
     PZZ370.
     HAZARDOUS SEAS WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     AFTERNOON FOR PZZ370.
     GALE WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY AFTERNOON FOR
     PZZ350.
     SMALL CRAFT ADVISORY FOR WINDS FROM 11 AM TO 11 PM PDT TUESDAY
     FOR PZZ350.
     HAZARDOUS SEAS WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
     AFTERNOON FOR PZZ350.

$$








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